The mechanism of transposition in E. coli will be investigated. In particular, we propose to investigate whether IS1 codes for polypeptides are involved in its transposition. We will attempt to determine whether IS1 codes for any polypeptides in a DNA-dependent protein synthesizing system, and whether it codes for any RNAs in a purified transcription system. The possible involvement of these gene products in the transposition of IS1 will be investigated by placing IS1 under control of the lambda PL promoter on a plasmid and asking whether transcription across IS1 from PL stimulates its transposition. Clones will be analyzed in which the IS1 has both orientations with respect to PL in order to investigate whether the putative IS1 polypeptides from one side or the other are involved. Two other projects will be undertaken. One is an attempt to detect a circular intermediate in the transposition of Tn5 by recombining the circular intermediate with a plasmid that carries part of Tn5. The detection of such an intermediate could provide key information on the mechanism of transposition. The other project is to determine whether transposition processes were responsible for the formation of some illegitimate lambda::pBR322 recombinants.